Rails 6.1 adds invert_where method

Rails 6.1 adds an invert_where method that will invert all scope conditions.

Let's see an example.

class User
  scope :active, -> { where(accepted: true, locked: false) }
end

>> User.all
=> #<ActiveRecord::Relation [
#<User id: 1, name: 'Rob', accepted: true, locked: true>
#<User id: 2, name: 'Jack', accepted: false, locked: false>
#<User id: 3, name: 'Nina', accepted: true, locked: false>
#<User id: 4, name: 'Oliver', accepted: false, locked: true>

Now let's query for active and inactive users

>> User.active
# SELECT * FROM Users WHERE `accepted` = 1 AND `locked` = 0
=> #<ActiveRecord::Relation [
#<User id: 3, name: 'Nina', accepted: true, locked: false>]>

>> User.active.invert_where
# SELECT * FROM Users WHERE NOT (`accepted` = 1 AND `locked` = 0)
=> #<ActiveRecord::Relation [
#<User id: 1, name: 'Rob', accepted: true, locked: true>
#<User id: 2, name: 'Jack', accepted: false, locked: false>
#<User id: 4, name: 'Oliver', accepted: false, locked: true>]>

As we can see above, if we use invert_where with multiple attributes, it applies logical NOR, which is NOT a OR NOT b, to the WHERE clause of the query. Using DeMorgan's Law, it can also be written as NOT (a AND b) to match the second output.

Check out the pull request for more details.